Conventional computer networking environments support the exchange of information and data between many interconnected computer systems using a variety of mechanisms. In an example computer networking environment such as the Internet, one or more client computer systems can operate client software applications that transmit data access requests using one or more data communications protocols over the computer network to server computer systems for receipt by server software application(s) executing on those servers. The server software application(s) receive and process the client data access requests and can prepare and transmit one or more responses back to the client computer systems for receipt by the client software applications. In this manner, software applications can effectively exchange data over a network using agreed-upon data formats.
One example of a conventional information exchange system that operates between computer systems over a computer network such as the Internet is provided by a set of applications and protocols collectively referred to as the World Wide Web. In a typical conventional implementation of the World Wide Web, client computer systems operate a client software application referred to as a web browser. A typical web browser operates to provide hypertext transport protocol (HTTP) requests for documents, referred to as “web pages,” over the computer network to web server computer systems. A web server software application operating in the web server computer system can receive and process an HTTP web page request and can return or “serve” a corresponding web page document or file specified (i.e., requested) in the client request back to the requesting client computer system over the computer network for receipt by the client's web browser. The web page is typically formatted in a markup language such as the hypertext markup language (HTML) or the extensible markup language (XML) that allows the web browser to receive and interpret the markup language information within the document in order to process the server response. The browser in the course of rendering the page on the computer screen may fetch more than one individual resource. Such client processing can include, for example, rendering information (or references to it) such as text, graphics or multimedia information to the user of the web browser on a display of the client computer system. A collection of related web page documents at a common network address or domain name is generally referred to as a web site.
In addition to simply accessing web pages, more recent conventional software and networking technologies that work in conjunction with protocols such as HTTP provide complete web-based applications or services, known as “web services”, over a computer network such as the Internet. Conventional web services architectures allow server-to-server connectivity for business applications.
In a conventional web services architecture, a server computer system can provide access to processing functionality using a web services interface that is defined in a machine-readable interface description, such as Web Services Description Language (WSDL). A particular service expressed or described in WSDL can provide some predefined and specific processing functionality. Other computer systems (e.g., other servers) that want to access web service functionality can discover and invoke the web service offered by the web services server by submitting requests for the service to the server using, for example, XML data encoded in a remote method invocation protocol such as the Simple Object Access Protocol (SOAP). A requesting computer system can transfer XML/SOAP requests to the server providing the web service over HTTP (or over secure HTTP, known as HTTPS). When a server receives an invocation of a web service via an XML message or stream of message encoded using SOAP/HTTP, the server decodes and process the XML encoded data, performs the web service processing (i.e., the application processing) on the decoded data, and can formulate an XML/SOAP/HTTP response. The server then returns the response to the requesting computer system (i.e., a client or another server) in XML format via HTTP. The XML/SOAP/HTTP web services computing paradigm thus allows distributed computing servers to share processing functionality with other computers, such as other servers and/or clients. Using web services, companies have found that enterprise applications can be interconnected in less time and at a lower cost with XML that is possible with conventional propriety middleware solutions.
Conventional XML processing technologies embedded within a web server allow the web server to interpret and process the XML-encoded data in a variety of ways. Several conventional XML technologies allow a software application to access (e.g., extract) XML-encoded data for application processing purposes. As an example, a server can use XML software processing technologies such as the Document Object Model (DOM) or Simple Application programming interface for XML (SAX) to parse XML encoded data (referred to sometimes as XML documents) to gain access to the XML encoded data. In addition, other XML-related technologies such as XPath and the eXtensible Stylesheet Transformation Language (XSLT) allow a developer of an XML-aware software application to define transformations of XML encoded data from one data format to another. Extensible Stylesheet Transformations (XSLT) is a language originally intended for converting, or transforming, documents written in XML into other formats, including HTML and other XML vocabularies. An XSL document is used to transform an XML document. A schema is a description in a metalanguage specifying the acceptable syntax or structure of an XML document. A schema document is used to validate an XML document and guarantee that its syntax is correct. Several schema languages exist. A filter is one or more XPath expressions (which may optionally be contained in an XSLT document or other overarching control structure) used to extract data from an XML document. This data can be used to produce a decision on the acceptability of the input XML document based on an arbitrary set of criteria as expressed in the query expressions. A filter verifies the input document based on semantic or other content (transformed or not transformed) not typically related to syntax, and so differs from a schema validation in this way.
An XSLT document can be used to transform an XML document, and also to schema validate the XML document at the same time using a schema specified in the XML document (or other out-of-band mechanism). As an example, a developer that creates an XML-aware application (e.g., for use on a web services server platform) can create an XSLT transformation to convert XML encoded data to HTML encoded data. A web server process that receives XML encoded data can apply such an XSLT transformation to the XML-encoded data to convert this data, for example, from XML to HTML and the server can return this data to the client thus allowing the client browser to render the XML-encoded data as HTML within a web browser.
If data security is a concern when performing transactions of XML encoded data between computer systems, conventional standards and common practices have emerged to allow a web server to use some of the above XML processing tools (e.g., DOM, SAX, etc.) to perform XML processing such as digital signature validation, encryption, and decryption upon XML encoded data.